The perception of effort: mind over muscle?

摘要

The concept that the perception of effort (i.e., effort sense) during exercise is not determined by sensory information from peripheral and visceral organs but rather by the conscious awareness of central motor commands is generally supported by the work highlighted by Marcpra (1). Indeed, similar conclusions may be drawn from studies in which effort sense has been manipulated by hypnotic suggestion (2, 3). For example, during constant-load cycling (e.g., peripheral and visceral afferent input remains relatively constant), the suggestion that one is cycling downhill has been shown to decrease an individual's rating of perceived exertion (RPE) while suggesting uphill cycling increases this rating (3). In addition, just imagining handgrip exercise has been shown to increase RPE almost to the same level as when exercise is actually performed (2). Under these unique experimental conditions, the perception of effort appears to be independent of feedback from skeletal muscle, heart, and lungs. In contrast, electrically induced exercise (i.e., no central motor command input) in patients with a hemisection of the spinal cord (Brown-Sequard syndrome) elicits larger increases in RPE when a leg with intact sensation is stimulated as compared to a leg with a sensory deficit (4). These data suggest that sensory input from skeletal muscle maintains the potential to modulate effort sense. As the performance of exercise requires the integration of multiple systems, it is likely that the perception of effort is determined by inputs both central and peripheral in origin.